Soldering on lithium batteries?

Guys, I have a few 3V AA-size batts from broken down CRV3's, but they don't have much of a + nipple and the - bottom does not protrude like normal AA's. They don't quite work in my setup and I was wondering if it was OK or safe to add a solder blob to the contacts? That is if I can find my soldering iron........Thanks...

Dan C

What about small disc magnets?

I know soldering to cells in general is a risky issue. Not sure how this applies to lithium primary cells, but I'm sure the hazards of soldering to Li-Ion cells apply. I would say it is riskier than soldering an alkaline or a NiCd cell.

On that note, if you clean and prep the surface, use a good flux, and are quick about your business, it can be done successfully and safely. Cooling the area as quickly as possible (blow on it or use some kind of cooling agent perhaps) is good. Soldering near the seal end (positive terminal in lithiums and NiCd/NiMH cells) is the riskiest.

Good luck!

I have done quick soldering on the + terminal without problems. Work fast and use a thin gauge solder for quicker melting. Plenty of folks have had to do this for the L4 application, I believe.

Wilkey

I'd suggest you practice beforehand until you can do it quickly. Roughen up the surface with some sandpaper (100grit). Wipe clean with rubbing alcohol and tissue paper. Apply flux. Melt a suitable size blob of solder on to the tip of your soldering iron. Touch said blob of solder to contact surface. Once you see the solder wet the surface, you can remove the soldering iron.

I don't know if putting the cells in the fridge to cool down, prior to the soldering operation, would help though my guess is that it will. I know that getting your soldering iron hotter than usual will help as the temperature gradient is more steep. I have a temperature controlled soldering iron. I put it to the 400 degC region, whereas I normal solder around 350degC.

I'd go with room temp cells because they won't act as a heat sink and soldering will be faster which is what you want. Additionally, condensation won't form where you want to solder. As mentioned, a light sanding, a little paste flux, first, at the solder location, and a hot iron (40-60watts) You won't have any problems if you keep the time to under five seconds. 2 - 3 seconds is, likely, all the time you'll need if you follow these guidelines. Been doing this for decades without one failure.

Thanks for the tips guys, with the info you've given me I believe I'll give it a shot......

Dan C

Yeah, if you count past 3 seconds and the blob of solder hasn't taken yet, you'd better stop and leave the cell for at least 10min to cool down. Get rid of the failed solder blob and start from scratch. If you leave the solder blob on, it will take longer for the entire lot to heat up.